Lee Jong-kul, a prominent lawmaker from President Moon Jae-in's Minjoo Party, last week told a seminar in Washington that South Korea may have to acquire nuclear weapons, an idea that until now has been confined to the conservative political fringes in Seoul.

"If North Korea continues to conduct nuclear weapon and missile tests while the North Korean nuclear negotiations are sluggish, South Korea should decide whether to break the principle of denuclearization and start developing nuclear weapons," Lee said in a speech at a forum in the U.S. capital sponsored by several Korea-related religious groups.

"An astronomical amount of money on armaments would be incurred to fight against nuclear weapons with non-nuclear weapons. It is clear that the most effective deterrent to nuclear weapons is a nuclear weapon itself," he stated. "Therefore, I believe that we need a phased strategy for nuclear armament. The first phase is to adopt highly effective weapon systems such as nuclear submarines, and the next phase is to promote the relocation of U.S. tactical nuclear weapons [to South Korea], and in the final phase, we should develop our own nuclear weapons."

The remarks appear to underscore the surprisingly muscular approach that the Moon administration is taking on defense issues despite its pursuit of an engagement policy with Pyongyang. Moon recently proposed that South Korea should increase its defense spending to 2.9 percent of gross domestic product, up from the current 2.4 percent, even as Seoul was proposing talks with North Korean on easing military tensions and reuniting separated families. "The new government is seeking a dialogue with North Korea, but it would be meaningless without the overwhelming national defense power," said Moon as quoted in a Blue House statement.

Lee's suggestion that South Korea may have to acquire nuclear weapons represents a dramatic reversal of his previous position. Lee, who served as Minjoo Party floor leader in the last National Assembly session, last year sharply condemned proposals for nuclear armament by some conservative lawmakers from then President Park Geun-hye's Saenuriparty, including his counterpart as National Assembly floor leader, Won Yoo-chul. Lee said that they "have brought up an irresponsible chauvinist nuclear armament theory. That is outdated nationalistic populism."

But Lee adopted a more somber tone in his Washington speech, saying that

"The nuclear and missile capabilities of North Korea…have been upgraded to pose serious threats. However, the international cooperation system to keep the North in check has been nullified," citing U.S.-China tensions over the U.S. deployment of the Terminal High Altitude Area Defense anti-missile system in South Korea.

Although Lee endorsed continued dialogue with Pyongyang, he warned that while the Moon administration "should inherit the basic principle of the Sunshine Policy,"it "needs to face the fact that North Korea's military capabilities have fundamentally changed since the Sunshine Policy period" of the previous decade as the Moon administration seeks to first freeze and then abolish the North's nuclear program.

What is particularly striking about Lee raising the idea of a nuclear option is that it indicates that this proposal is now being debated within "progressive" Korean political circles as well as conservative ones.

Attention has recently focused, for example, on Moon's support for a fleet of nuclear-powered submarines to counter North Korea's submarine-launched ballistic missile capability. This has raised concerns among the international non-proliferation community that the development of an enrichment capability for fueling nuclear submarines would also give South Korea the capability to build nuclear weapons.

The willingness of those affiliated with the Moon administration to even consider a nuclear option may reflect uncertainty over the Trump administration's commitment to defending South Korea in face of a North Korean threat and as well as a desire by Moon to create an independent military capability less reliant on the U.S.

But continued discussions about a nuclear option for South Korea could also be seen as a signaling mechanism by Seoul to persuade Washington and Beijing to do more to curb North Korea's nuclear program or seek reassurance from the U.S. on security guarantees.

For example, Hong Hyunik a senior research fellow at the Sejong Institute in Seoul, told the forum that U.S. tactical nuclear weapons should be reintroduced to South Korea, which were removed in 1991, because THAAD was "useless" as a deterrent in stopping a North Korea missile attack. He said that the presence of U.S. nuclear weapons would force North Korea to resume negotiations on the dismantlement of its nuclear and missile program, with one possible outcome being that North Korea could acquire a security guarantee by being placed under the nuclear umbrella of either China or Russia like that provided by the U.S. for South Korea.

John Burton, a former Korea correspondent for the Financial Times, is now a Washington,D.C.-based journalist and consultant. He can be reached at johnburtonft@yahoo.com.